Flyable folding fin

Abstract

A method and apparatus for flying a folding fin from a stored folded position on a flight vehicle housing to a deployed erect position, using available aerodynamic or fluid forces to control the fin deployment. The fin is erected in several stages. First, a hinge spring bias or lifting wedge means, or combination of fin and body shape, raises the fin surface sufficiently to engage the high-speed fluid flow over the vehicle housing. Next, a motion sensor measures the fin erection angle. Finally, a feedback control system adjusts the fin control angle to increase or reduce the time rate of change of fin erection angle, as necessary. In this manner, the fin can be "flown" into its deployed position in a smooth and controlled manner whereupon it is locked into the deployed erect position on the vehicle housing. A flyable folding fin apparatus having a fixed hinge line has the additional advantage of providing vehicle stabilization immediately following launch because an independently controlled movable surface in the foldable fin assembly can be deflected without aerodynamic assistance to provide a stable aerodynamic shape immediately. Once the flight vehicle is in stable flight, this fixed hinge line fin assembly can then be erected similarly to the movable hinge line fin embodiment.

We claim: 
     
       1. A fin erector apparatus for extending a movable fin from a stored position to a deployed position on a vehicle housing, said apparatus comprising: control shaft means in said vehicle housing, having a first axis of rotation, for rotatably attaching said movable fin to said vehicle housing;   sensor means for creating a deployment position signal in response to the position of said movable fin;   control processor means for generating a control output signal in response to said deployment position signal;   hinge means in said movable fin, having a second axis of rotation, for pivotally attaching said movable fin to said control shaft means; and   drive motor means for applying a torque to said control shaft means in response to said control output signal.   
     
     
       2. The fin erector apparatus described in claim 1 wherein: said control processor means further comprises rate processor means for modifying said control output signal in response to the time rate of change of said deployment position signal.   
     
     
       3. The fin erector apparatus described in claim 2 wherein: said deployment position signal is representative of the erection angle of said movable fin about said second axis of rotation.   
     
     
       4. The fin erector apparatus described in claim 1 further comprising: deployment locking means for locking said movable fin in said deployed position.   
     
     
       5. The fin erector apparatus described in claim 1 wherein: said first axis of rotation is disposed in substantial orthogonality to said second axis of rotation.   
     
     
       6. The fin erector apparatus described in claim 1 further comprising: lifting assist means mounted on said vehicle housing for lifting an edge of said movable fin from said housing in response to rotation of said control shaft means about said first axis of rotation.   
     
     
       7. A fin erector apparatus for extending a movable fin assembly from a stored position to a deployed position on a vehicle housing, said apparatus comprising: a controlled movable surface in said movable fin assembly;   first hinge means in said movable fin assembly, having a first axis of rotation, for pivotally attaching said controlled movable surface to said movable fin assembly;   second hinge means in said vehicle housing, having a second axis of rotation, for pivotally attaching said movable fin assembly to said vehicle housing;   sensor means for creating a deployment position signal in response to the position of said movable fin assembly;   control processor means for generating a control output signal in response to said deployment position signal; and   drive motor means for applying a force to said controlled movable surface in response to said control output signal.   
     
     
       8. The fin erector apparatus described in claim 7 wherein: said control processor means further comprises rate processor means for modifying said control output signal in response to the time rate of change of said first position signal.   
     
     
       9. The fin erector apparatus described in claim 8 wherein: said deployment position signal is representative of the erection angle of said movable fin assembly about said second axis of rotation.   
     
     
       10. The fin erector apparatus described in claim 7 wherein: said first axis of rotation is disposed in substantial orthogonality to said second axis of rotation.   
     
     
       11. The fin erector apparatus described in claim 7 further comprising: deployment locking means for locking said moveable fin assembly in said depolyed position.   
     
     
       12. A method for erecting a folding fin from a storage position to a deployed position on an air flight vehicle housing having a fluid flow along said vehicle housing, said folding fin having a control angle position about a first axis of rotation and an erection angle position about a second axis of rotation, comprising the steps of: initiating fin deployment to expose the surface of said folding fin to said fluid flow; and   performing repeatedly, until said folding fin is in said deployed position, the steps of   computing the time rate of change of said erection angle position,   computing an erection angle velocity error by subtracting said erection angle time rate of change from a predetermined angular velocity,   computing a control angle correction to said control angle position for reducing said erection angle velocity error to zero, and   rotating said movable hinge line about said first axis of rotation by said control angle correction.   
     
     
       13. The erecting method described in claim 12 further comprising the subsequent step of: locking said folding fin in said deployed position.   
     
     
       14. A method for erecting a folding fin assembly from a storage position to a deployed position on a flight vehicle housing having a fluid flow along said vehicle housing, said folding fin assembly having a controlled movable surface having a control angle position about a first axis of rotation and an erection angle position about a second axis of rotation, comprising the steps of: initiating fin deployment to expose the surface of said folding fin assembly to said fluid flow; and   performing repeatedly, until such folding fin assembly is in said deployed position, the steps of   computing the time rate of change of said erection angle position,   computing an erection angle velocity error by subtracting said erection angle position time rate of change from a predetermined angular velocity,   computing a control angle correction to said control angle position for reducing said erection angle velocity error to zero, and   rotating said controlled movable surface about said first axis of rotation by said control angle correction.   
     
     
       15. The erecting method described in claim 14 further comprising the subsequent step of: locking said folding fin assembly in said deployed position.